Air filter



FIG. 1 is a perspective view of an air filter, showing my new desgin;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left elevational view thereof;

FIG. 5 is a right elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof. 

The ornamental design for an air filter, as shown. 